when does your boost start?

[gcorky]

as title peeps,plz could you briefly describe yoursetup and character of your car i.e laggy,boost start high rpm etc.

[lentec]

As soon as i hit the pedal

Supercharged 2.7e.

[Omi]

Probably about May.

[Jon_Bmw]

About 2000 rpm, i'm on full boost(8spi) which runs all the way up to redline, makes for a very torquey car for sure. Pulls like a train in any gear. This is due to a small turbo, but you can search under my name for full details of it i'm sure.

[fuzzy]

mine comes on at 1500rpm and runs up to 18psi but drops back to 15 psi.with the right injectors it will run up to 28psi. thats a cosworth stage 3, t34 turbo.not really relevant to your set up i know,but good any way

[e30_Turbo]

I start spooling @ 1800 rpms, by 2300 I hit 9psi and by 2500 I'm sitting @ 15psi, which decays to about 12psi @ 5k+.

My setup seems to be more for a quick getaway than a top end monster, so bigger compressor and a welded and fresh head should see me holding max psi till redline

I stayed level pegging with a audi RS6 from 50-100mph, but needed more top end power to stay with him after that, dam those things are quick but he did give the usual "WTF??" look

[gcorky]

some high pressures here

[NICKE30CAB]

Probably about May.

lol

[Turbo-Brown]

Yay! I an post an answer to this one now

Not really full bored mine yet, but on probably half throttle, the boost starts at around 2800rpm.

Off boost it's no different to an N/A car so around town's a doddle.

Setup's a twin turbo, twin intercooler and 6 throttles with Emerald controlling the show.

[gcorky]

Yay! I an post an answer to this one now

Not really full bored mine yet, but on probably half throttle, the boost starts at around 2800rpm.

Off boost it's no different to an N/A car so around town's a doddle.

Setup's a twin turbo, twin intercooler and 6 throttles with Emerald controlling the show.

so more is better for you turbo-brown eh??????twin turbo ,6 throttles ,twin ic....yikes man.
which turbos you run ,whats it like or are ya still tweaking?how have you configured the coolers ?

[Turbo-Brown]

more is always more (trouble)

The turbos are little T25s from a skyline (I think) They seem to have quite big compressor housings (AR.42) but little turbine housings (AR.48)

The intercoolers are run in parallel so each turbo feeds into one IC of it's own, then the ICs exit into the plenum.

I'm really chuffed with the way it drives actually. It's pretty smooth around town and gives reasonable off boost acceleration and then a nice kick up the arse when you tickle it a bit

Can see why Fozzy keeps turning the wick up on his!

[gcorky]

hehehhehehheh kick up the arse,very good m8 what kinda figure u lookin at ???bhp

[Turbo-Brown]

Really haven't got a clue at the moment, but based on a very simple pressure ratio calculation, it should be making around 250bhp with 0.5bar of boost.

Air temps don't seem to be an issue (for some reason they drop with the boost on! ) so going up to 0.6bar shouldn't be a problem hopefully which if I'm very lucky might net me around 270bhp.

Still, got 500 miles of running in to do before it goes on the RR for full mapping

[fuzzy]

is there a ratio of how much bhp you get from each psi you raise boost or is at all engine specific? :?altough i notice your expecting about 20bhp from approx 1.5psi.

[Turbo-Brown]

Yeah kind of, the assumption is that the engine could make 170bhp at atmospheric pressure which is 1bar give or take.

With an additional 0.5 bar of pressure in the manifold, the engine should consume 1.5 times the air it could with only atmospheric pressure and as air consumption is directly proportional to power, this should give 1.5 times the power so:

170*1.5=255

The amount of power you get for each psi depends on what you started with N/A in the first place so if you had a 100bhp engine with 0.5bar of boost, you should see 150bhp or an extra 6.8bhp/psi. If you had a 200bhp engine with the same 0.5bar, you'd hopefully get 300 13.6bhp/psi.